Inflator device ignition of gas generant

ABSTRACT

Inflator device assemblies wherein an igniter composition used to ignite an associated gas generant material is provided on a selected surface, such as on a damper pad, within the inflator device. Suitable igniter compositions may include a silicone resin additive effective to adhere the igniter composition to a surface within the inflator device.

BACKGROUND OF THE INVENTION

This invention relates generally to the ignition of combustiblematerials and, more particularly, to ignition of gas generant materialssuch as used in inflator devices used for the inflation of inflatablerestraint airbag cushions.

It is well known to protect a vehicle occupant using a cushion or bag,e.g., an “airbag,” that is inflated or expanded with gas when thevehicle encounters sudden deceleration, such as in a collision. In suchsystems, the airbag cushion is normally housed in an uninflated andfolded condition to minimize space requirements. Upon actuation of thesystem, the cushion begins being inflated in a matter of no more than afew milliseconds with gas produced or supplied by a device commonlyreferred to as an “inflator.”

Many types of inflator devices have been disclosed in the art for use inthe inflating of one or more inflatable restraint system airbagcushions. Many prior art inflator devices include solid form gasgenerant materials which are burned to produce or form gas used in theinflation of an associated airbag cushion.

Such inflator devices tend to involve rather complex ignition processes.For example, it is relatively common to employ an electrically initiatedsquib to ignite a separate charge of an igniter composition. Theproducts of such ignition are then used to ignite the gas generantmaterial. In practice, the ignition process of many various priorinflator devices require such a separate igniter charge because thesquib does not itself generally supply sufficient hot gas, condensedphase particles or other ignition products to heat the gas generantmaterial to result in the reaction of the material such as to result indesired gas generation.

FIG. 1 illustrates an inflator device or assembly generally designatedby the reference numeral 10 and such as is known in the prior art. Theinflator assembly 10 has a generally cylindrical external outline andincludes a housing construction 12 such as formed of two structuralcomponents, i.e., a lower shell or base portion 14 and an upper shell ordiffuser cap portion 16, such as may desirably be made of steel andappropriately joined or fastened together such as by application of aninertia welding operation. The housing 12 is illustrated in the generalform of a flattened, disk-shaped circular cylinder typically orgenerally having a length to diameter ratio of about 0.5 or less. Itwill be appreciated that such a sized and shaped housing may mostconveniently correspond to the shape of the vehicle steering wheel andcan therefore facilitate assembly in an aesthetically pleasing manner.

The diffuser cap portion 16 is in the general form of an inverted bowland includes a top wall 18 and a cylindrical sidewall 20. The sidewall20 includes a plurality of spaced, preferably, generally uniformlyspaced gas exit ports 22.

The base portion 14 includes a mounting opening 24, the use of whichwill be discussed in greater detail below. The base portion 14 alsoincludes a peripheral bracket 28 that extends radially outward from thehousing 12 and serves to form an interface attachment which is used toattach the inflator assembly 10 to a vehicle, the occupants of which areto be protected from injury such as may result from the impact of acollision.

The housing 12 is configured to define a generally cylindrical chamber30. The chamber 30 contains or houses a supply of a gas generantmaterial 32, such as composed of a pyrotechnic, such as known in theart, in a desired selected form. In FIG. 1, the gas generant 32 is shownas contained in the chamber 30 in a tablet form but other forms, such asknown in the art may be used. Surrounding the gas generant material 32is a filter assembly 34 such as includes a cooling screen or filter suchas formed of multiple layers or wraps of metal screen.

The inflator assembly 10 also includes a retainer assembly 36 such ascomposed of a retainer 38 and annular-shaped diffuser and base damperpads, 40 and 42, respectively, and such as serving as constructionexpedients. For example, the inclusion of such a retainer assembly orspecific components thereof may be useful and desired to retain theinflator assembly components in proper relative arrangement, preventundesired gas flow passage through the assembly and/or minimize or avoidundesired contact of the gas generant within the assembly 10 such as maycreate undesired rattle or noise should the assembly be subjected tocertain vibrations or other movements or forces. In practice, suchdamper pad elements are commonly composed or fabricated of a glass fibermaterial or the like.

Surrounding the filter 34 and generally adjacent the inner surface ofthe sidewall 20 is an adhesive-backed foil seal 44 which preferablyhermetically seals the gas generant material 32 within the inflator 10,thereby protecting the gas generant material from possibly damagingambient conditions, such as including moisture.

An igniter assembly, generally designated by the reference numeral 48,is mounted to the housing 12 in a location within the chamber 30 via themounting opening 24. The igniter assembly 48 may take the form of aknown pyrotechnic initiator device such as includes, as are known in theart, an igniter cup 50 having an interior 51 wherein is housed anigniter material 52, an igniter device or squib 54, and a squib adapteror holder 56 whereby the igniter assembly 48 is mounted to or mated withthe housing 12. As shown, the igniter cup 50 and associated componentsof the igniter assembly 48 are inserted or fitted into or through anigniter tube 58. The igniter tube 58 can be formed of a gas-impermeablematerial, e.g., a metal such as plain carbon steel, and includes aplurality of spaced apart exit orifices 60 wherethrough products ofignition can be passed through and directed into contact with the gasgenerant material 32 to effect ignition and reaction thereof.

When actuated, the squib 54 causes ignition of the igniter material 52which customarily results in an increase in pressure within the cupinterior 51 with the subsequent predetermined rupturing or opening ofthe igniter cup 50 to permit passage, through the exit orifices 60, ofignition products produced by the combustion of the igniter material 52.With such passage, the ignition products are put into contact with thegas generant material 32 contained within the inflator chamber 30 suchas to result in the ignition and reaction of the gas generant material32. The gas generant material thus reacts to produce gas. The gas soproduced passes through the filter 34, rupturing the foil seal 44 andpassing through the gas exit ports 22 and out from the inflator assembly10 into an associated airbag cushion (not shown). As will beappreciated, the contact of ignition products with the gas generantmaterial can appropriately be, either or both, thermal or physical innature.

In practice, the igniter assembly 48 can be formed by placing theigniter cup 50 containing the igniter material 52 over the igniterdevice/squib 54 and the holder 56. The igniter assembly 48 can bedesirably placed at the mounting opening 24, such as with the ignitertube 58 in press fit relationship therewith, and joined to the housing12 such as by welding the holder 56 to the base portion 14 at themounting opening 24.

Such igniter charges have also been used in various dual stage oradaptive inflator assemblies. For example, FIG. 2 illustrates a dualstage or adaptive output inflator device or assembly generallydesignated by the reference numeral 210, such as generally disclosed incommonly assigned, co-pending U.S. patent application Ser. No.09/465,082, the disclosure of which is hereby incorporated by reference.The inflator assembly 210 has various features in common with theinflator assembly 10, described above. In particular, the inflatorassembly 210 has a generally cylindrical external outline and includes ahousing construction 212 such as formed of a lower shell or base portion214 and an upper shell or diffuser cap portion 216 and in the generalform of a flattened, disk-shaped circular cylinder.

The diffuser cap portion 216 includes a top wall 218 and a cylindricalsidewall 220. The sidewall 220 includes a plurality of spaced gas exitports 222. The base portion 214, in addition to a first mounting opening224, however, also includes a second mounting opening 226. The baseportion 214 includes a radially outward extending peripheral mounting orattachment bracket 228.

The housing 212 is configured to define a generally cylindrical firstchamber 230 which contains or houses a supply of a first gas generantmaterial 232, such as composed of a pyrotechnic. While the gas generantmaterial 232 is shown in an extruded cylindrical perforated solid form,e.g., in the form of solids which include a cylindrical bore such thatthe gas generant material is generally tubular in shape, gas generant inother suitable forms can be used. Surrounding the gas generant material232 is a filter assembly 234 such as includes a cooling screen or filtersuch as formed of multiple layers or wraps of metal screen.

The inflator assembly 210 also includes a retainer assembly 236 such ascomposed of a retainer 238, a diffuser damper pad 240 and a base damperpad 242. A foil seal 244, generally adjacent the inner surface of thesidewall 220, seals the gas generant material 232 within the inflator210.

A first igniter assembly, generally designated by the reference numeral248 and similar to the igniter assembly 48 described above, is mountedto the housing 212 in a location within the first chamber 230 via themounting opening 224. The first igniter assembly 248 includes an ignitercup 250 having an interior 251 wherein is housed a supply of ignitermaterial 252, an igniter device or squib 254, and a squib adapter orholder 256 whereby the igniter assembly 248 is mounted to or mated withthe housing 212. The igniter cup 250 and associated components of theigniter assembly 248 are inserted or fitted into or through an ignitertube 258. The igniter tube 258, similar to the igniter tube 58 includesexit orifices (not shown) wherethrough products of ignition can bepassed through and directed into contact with the gas generant material232 to effect ignition and reaction thereof.

The first chamber 230 also houses or contains a second chamber 262. Itis with respect to this second chamber and the construction andoperation thereof that the inflator assembly 210 differs mostsignificantly from the inflator assembly 10 described above. The secondchamber 262 includes a generant cup 264, a lid closure 265, a secondigniter device or squib 266, and a second squib adapter 268 whereby thesecond chamber 262 is mounted to or mates with the housing 212 at thesecond mounting opening 226.

The generant cup 264 and the lid closure 265 cooperate to form agenerant cup interior 270 wherein desirably placed is a selectedquantity of a second gas generant material 272. The second gas generantmaterial 272 may typically be in the form of a pyrotechnic material andmay be either the same or different in composition, shape, size or form,as compared to the first gas generant material 232.

The generant cup 264 desirably includes a generally cylindrical sidewall274 and such as preferably includes a shoulder portion 276 such asformed therein. The lid closure 265 and the shoulder portion 276 maydesirably form a press or interference fit form of attachment when in astatic state or condition. The generant cup 264 and the lid closure 265cooperate and function in a manner such as to prevent the combustionproducts resulting upon actuation of the first igniter device 254, toenter into the second chamber 262. Further, the generant cup 264 and thelid closure 265 desirably cooperate and function in a manner such as topermit the combustion products formed by reaction of the gas generantmaterial contained within the second chamber 262, when properly anddesirably actuated, to pass from the second chamber 262 out into thefirst chamber 230 and subsequently through the filter assembly 234 andout through the exit ports 222 into an associated airbag cushion (notshown).

For example, in a typical deployment operation involving actuation andfiring of the second chamber 262, actuation of the second igniter squib266 results in sufficient discharge to ignite at least some of thesecond gas generant material 272. The ignition and reaction of thesecond gas generant material in turn produces or results in sufficientpressure within the second chamber 262 to dislodge the lid closure 265from the shoulder portion 276 such as to open the second chamber 262 toentry of combustion products formed by or as a result of actuation ofthe first chamber 230. Entry into the second chamber of such combustionproducts desirably can result in the more complete or full combustion ofthe remaining second gas generant material.

A common means of obtaining substantially simultaneously ignition of anextended length of an igniter composition charge is by means of anignition cord. In practice, however, it is common that such a length ofignitor cord be housed or contained within an igniter tube extendingwithin such an igniter charge.

While ignition of a gas generant material may ultimately be achievedthrough such the inclusion and use of an igniter charge, such assembliesand associated uses tend to undesirably complicate the ignition processas well as to complicate the manufacture, production and design of theassociated inflator device. For example, such uses typically necessitatethe manufacture of a container or other storage device to hold or storethe igniter composition and then the incorporation of such a storagecontainer in the inflator device. As will be appreciated, theincorporation and use of such an ignition process can detrimentallyimpact either or both the weight and cost of the corresponding apparatushardware. Further, space is often at a premium in modem vehicle design.Consequently, it is generally desired that the space requirements forvarious vehicular components, including inflatable vehicle occupantrestraint systems, be reduced or minimized to as great an extent aspossible. The incorporation of an igniter assembly such as describedabove and associated support structures, may require a larger thandesired volume of space within an associated inflator device. Inparticular, such volume of space could potentially be utilized to storeor contain gas generant material and thereby permit the volume of spacerequired by the inflator device to be reduced.

Thus, there is a need and a demand for alternative airbag inflatordevice ignition schemes and, in particular, there is a need and a demandfor avoiding the requirement or inclusion of separate ignitercomposition charges and associated ignition trains or hardware. Oneapproach discussed in the prior art has been to apply a coating of anigniter formulation directly on a gas generant material. For example,various patents, including U.S. Pat. Nos. 4,698,107; 4,806,180; and5,034,070, disclose processing wherein an ignition coating is applied,such as in the form of a liquid or a water slurry, to azide-based gasgenerant materials. Such processing typically necessitates first theformation of the azide-based gas generant, including the proper formingand drying of gas generant grains in selected shapes, followed by thecoating of the grain with a wet slurry of the ignition material, such asby immersion of the grain in a slurry of the coating material, and thenfinal drying.

In such dip coat processing, generally either individual gas generanttablets or wafers are coated as they go through a coating slurry on aconveyer belt, or the gas generant tablets or wafers are put in bulkcontainers and submerged in the slurried coating material. These typesof process are typically relatively slow and may lead to problems suchas coated tablets/wafers sticking either or both to themselves andassociated equipment, such as conveyer belts.

In addition, dependent on the shape of the gas generant tablet or waferthere may also be a problem in obtaining application of a uniformcoating. For example, if the gas generant material has a relatively flatform, the slurry coating may tend to pool and may therefore dry to forma coating of variable thicknesses.

Also, dip coating equipment (e.g., dip baskets and conveyer belts) mayeasily be contaminated with igniter material, leading to potential orincreased safety concerns.

In view of the above, there is a need and a demand for materials andprocessing techniques such as may facilitate or permit the inclusion ofan igniter composition within an inflator device, such as the placementof an ignition composition onto a gas generant material having aselected form or to a non-gas generant surface within an inflatordevice, for example.

SUMMARY OF THE INVENTION

A general object of the invention is to provide improved ignitercompositions, inflator devices and methods for including an ignitermaterial within an inflator device.

A more specific objective of the invention is to overcome one or more ofthe problems described above.

The general object of the invention can be attained, at least in part,through an improvement in igniter compositions used to ignite a gasgenerant material within an inflator device. As detailed below, suchimprovement in accordance with one embodiment of the invention involvesincluding, in the igniter composition, a silicone resin additiveeffective to adhere the igniter composition to a surface within theinflator device.

The prior art generally fails to provide inflator device assemblies andigniter compositions useable therein which can operate as effectively asmay be desired without including or requiring additional hardware suchas igniter tubes, igniter cup assemblies or the like to hold or containsuch igniter materials. At least partially as a result thereof, theprior art has generally failed to provide inflator device assemblieshaving a design of one or more of desired simplicity of constructionand/or operation, reduced weight and reduced cost.

The invention further comprehends an improvement in an airbag inflatordevice which contains a quantity of gas generant material reactable toproduce gas for inflation of an associated inflatable device and aquantity of an igniter material reactable to ignite at least a portionof the quantity of gas generant material. In accordance with onepreferred embodiment of the invention, such improvement relates to theinclusion within the inflator device of a damper pad onto which pad atleast a portion of the quantity of igniter material forms a coating.

The invention still further comprehends a method of including an ignitermaterial within an inflator device. Such method, in accordance with onepreferred embodiment of the invention, involves applying an ignitermaterial composition which includes an igniter fuel, an igniter oxidizerand a silicone resin additive effective to adhere the igniter materialcomposition to an inner surface of the inflator device.

The invention yet still further comprehends a method of providing anigniter material for inclusion within an inflator device which containsat least one damper pad. In particular, such method includes coating adamper pad substrate with an igniter material composition which includesan igniter fuel, an igniter oxidizer and an additive effective to adherethe igniter material composition to the damper pad substrate.

Other objects and advantages will be apparent to those skilled in theart from the following detailed description taken in conjunction withthe appended claims and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified cross sectional view of a single stage inflatordevice as is known in the prior art.

FIG. 2 is a simplified cross sectional view of a dual stage inflatordevice as is known in the prior art.

FIG. 3 is a simplified cross sectional view of a single stage inflatordevice in accordance with one embodiment of the invention.

FIG. 4 is a simplified cross sectional view of a dual stage inflatordevice in accordance with one embodiment of the invention.

FIG. 5 is a simplified cross sectional view of a single stage inflatordevice, similar to the inflator device shown in FIG. 3 but now showingor identifying alternative surface locations to which a coating of anigniter composition in accordance with the invention can be applied.

FIG. 6 is a simplified cross sectional view of a dual stage inflatordevice, similar to the inflator device shown in FIG. 4 but now showingor identifying alternative surface locations to which a coating of anigniter composition in accordance with the invention can be applied.

FIG. 7 is a graphical depiction of combustion chamber pressure as afunction of time performance realized with the test inflator in Example3 and Comparative Example 5.

FIG. 8 is a graphical depiction of tank pressure as a function of timeperformance realized with the test inflator in Example 4.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides improved igniter compositions, inflatordevices and methods for including an igniter material within an inflatordevice such as suitable for use in the inflation of an inflatable devicesuch as a vehicle occupant restraint airbag cushion. The inventioncontemplates such igniter compositions which include a silicone resinadditive effective to adhere the igniter composition to a surface withinthe inflator device.

As will be described in greater detail below and in accordance withcertain preferred embodiment of the invention, subject ignitercompositions can desirably be applied such in the form of a coating ontothe surface of the gas generant material. In at least certain otherpreferred embodiments of the invention, however, subject ignitercompositions can desirably be applied to one or more non-gas generantsurfaces within the inflator device, including, for example, damperpads, igniter cords and the like.

In accordance with a preferred practice of the invention, preferredsilicone resin additives for use in the practice of the inventiondesirably function as a binder. That is, preferred silicone resinadditives for use in the practice of the invention can desirably serveto bind together other components of the igniter composition. Forexample, preferred silicone resin additives can desirably serve to bindtogether two or more of an igniter fuel material, an igniter oxidizermaterial or performance additive material such as in the form of a metaloxide such as may be included to improve either or both slag formationor bum rate properties or qualitites.

Preferred silicone resin additives for use in the practice of theinvention are typically composed of a plurality of polysiloxane chains,such as of various molecular weights. For example, useful silicone resinadditives include those composed of polysiloxane chains which havemolecular weights in the range of 8000 to 80,000 grams per mole. As willbe appreciated, useful silicone resins may contain or include variouschemical groups such as methyl (CH₃), phenyl (C₆H₆) and propyl(CH₂CH₂CH₃), for example, bound to such polysiloxane backbone. Suchresins are commonly identified as hydroxyl functional meaning that theyinclude or contain a hydroxyl content (such as in the form of a silanolgroup) that desirably can undergo a condensation reaction such as toeffect further or additional chain elongation and/or crosslinking. Inpractice, the use of such silicone resin additives having hydroxylcontents in the range of about 1% to about 10% by weight of resinmaterial has been found useful in resulting in formulations which canconveniently provide or result in desired surface coverage upon theapplication of corresponding formulations. Further, while usefulsilicone resin additives may include or contain various contents ofsilicon bound to oxygen, in practice it is generally preferred thatbetween about 60% and 75% of the silicon bonds contained in the resinadditive be with or to oxygen atoms.

Specific silicone resin additives which may be used in the practice ofthe invention include: Dow Coming 6-2230 silicone resin of the DowCorning Corporation; Wacker SilRes REN 100 silicone resin of WackerSilicones Corporation of Wacker-Chemie GmbH; and General Electric SR355silicone resin of GE Silicones of General Electric Company, for example.

As identified above, preferred silicone resin additives for use in thepractice of the invention also desirably function as an adhesiveeffective to adhere the balance of an igniter composition to a surfacewithin the inflator device. In one preferred embodiment of theinvention, the desired silicone resin additive is added to a suspensionof igniter components in a suitable organic solvent, such as a solventselected from the group of solvents consisting of alcohols, ketones,esters, aromatics and chlorinated organics. Ethanol and acetone areexamples of quick drying organic solvents which, in accordance withcertain preferred embodiments of the invention, are suitable for use inthe practice of the invention.

The resin additive dissolves in the organic solvent and, in combinationwith the igniter components, a suspension is formed. The suspension canthen be applied, desirably in the form of a coating of relative uniformthickness, onto a surface (sometimes referred herein as a “targetsurface”) such as may occur or be present within a particular inflatordevice. As the organic solvent evaporates, the resin additive becomestacky and serves to bind or adhere the balance of the ignitercomposition to the target surface. Upon completion of the dryingprocess, a strong bond or otherwise effective joining or adhesion isformed between the igniter composition and the target surface. Thepreferred practice of the invention results in the desired adhesion orjoining of the igniter material to the selected target surface withoutdetrimentally impacting the ignitability of igniter material.

Further, in order to provide or result in suitable adherability for theigniter composition to a desired or selected target surface within aninflator device, preferred silicone resin additives for use in thepractice of the invention have a solubility of at least one gram per 100ml of organic solvent. In practice, preferred organic solvents areselected from the group of solvents consisting of alcohols, ketones,esters, aromatics and chlorinated organics.

While the amount of silicone resin additive required for the desiredfunctioning in the practice of the invention can vary dependent onfactors such as the specific composition of the particular ignitermaterial, it has been found generally desirable to include the selectedsilicone resin additive in such an igniter composition in a relativeamount of at least about 1 wt. % to no more than about 10 wt. %, basedon the total composition weight of the igniter material (e.g., fuel,oxidizer and any other additives) and the silicone resin additive.

While the broader practice of the invention is not limited to theinclusion and use of silicone resin additives to specific ignitercompositions, the inclusion and use of silicone resin additives inaccordance with the invention has been found particularly useful orpractical with certain igniter compositions or certain ignitercomposition component materials.

In view thereof, particularly preferred igniter compositions for use inthe practice of the invention include, as a primary fuel component analloy of aluminum and magnesium (herein sometimes referred to as an“Al/Mg alloy”). It has been found that increasing the magnesium contentof such fuel component generally results in the formulation havingincreased ignitability as well as increased sensitivity to impact,friction and electrostatic discharge. In view of the increasedsensitivity of higher magnesium content formulations, an Al/Mg alloywhich contains about 50 to about 90 wt. % Al and about 10 to about 50wt. % Mg, preferably about 50 to about 80 wt. % Al and about 20 to about50 wt. % Mg and, at least in certain preferred embodiments, morepreferably an Al content of about 70 percent and a Mg content of about30 percent, will generally be preferred. In accordance with certainpreferred embodiments of the invention, between about 10 to about 60weight percent of the silicone resin additive-containing ignitercomposition generally constitutes such an Al/Mg alloy fuel component.

Further, preferred igniter compositions for use in the practice of theinvention include an oxidizer component such as composed of strontiumnitrate, an alkali metal nitrate (such as potassium nitrate, forexample) or a combination thereof. It has been found generally desirablethat the major oxidizer component be selected to assist in producing aneasily filterable combustion product slag. In accordance with onepreferred embodiment of the invention, at least about 50 wt. % up to 100wt. % of the oxidizer component of the subject igniter compositioncomprises strontium nitrate. Strontium nitrate has been found todesirably produce condensible combustion products, such as strontiumoxide, which have a relatively high-melting point. As will beappreciated, such high-melting temperature condensible combustionproducts can generally more easily be filtered or otherwise removed fromthe inflation gases produced or formed by an associated inflator device,as compared to igniter compositions, such as standard boron potassiumnitrate, which produce or form low-melting temperature combustionproducts in relatively greater proportion.

Thus, an igniter composition in accordance with one preferred embodimentof the invention includes:

at least about 10 wt. % and no more than about 60 wt. % of an Al/Mgalloy igniter fuel;

at least about 30 wt. % and no more than about 80 wt. % of an igniteroxidizer selected from the group consisting of strontium nitrate, alkalimetal nitrates and combinations thereof; and

at least about 1 wt. % and no more than about 10 wt. % of a siliconeresin additive effective to adhere the igniter composition to a surfacewithin the inflator device, as described above.

As identified above, subject igniter compositions can desirably beapplied such in the form of a coating onto the surface of the gasgenerant material. In at least certain other preferred embodiments ofthe invention, however, subject igniter compositions can desirably beapplied to one or more non-gas generant surface within the inflatordevice, including, for example, damper pads, igniter cords and the like.Further, as will be appreciated, preferred target surfaces for use inthe practice of invention are surfaces which already exist or arepresent within an inflator assembly. Through such use of an existingsurface, igniter compositions in accordance with the invention can beincluded with desired inflator assemblies without requiring addedelements to the assembly. Consequently and as further described below,the inflator assembly inclusion and use of such igniter compositions candesirably simplify the construction of the associated inflator assembly.Though such simplification, one or more of the cost, weight, size and/orperformance dependability of the resulting inflator assembly can befavorably altered.

Practice and application of the invention, as well as at least some ofthe advantages associated or connected therewith, will be discussed inconnection with FIGS. 3-8.

FIG. 3 shows a simplified view of a single stage inflator device orassembly 310, in accordance with one embodiment of the invention. Whilethe inflator assembly 310 is many respects similar to the inflator 10described above, the inflator assembly 310 is significantly simplifiedin either or both construction and operation. In particular, theinflator assembly 310 avoids the need for an igniter cup (to hold orcontain an igniter material), an igniter tube (wherethrough products ofignition can be passed through and directed into contact with anassociated supply of gas generant material to effect ignition andreaction thereof) or a retainer (to hold or retain either of both suchan igniter cup and igniter tube in a particular relative arrangementwithin an inflator assembly).

The inflator assembly 310, similar to the inflator 10, has a generallycylindrical external outline and includes a housing construction 312such as formed of two structural components, i.e., a lower shell or baseportion 314 and an upper shell or diffuser cap portion 316, such as maydesirably be made of steel and appropriately joined or fastened togethersuch as by application of an inertia welding operation. The housing 312is illustrated in the general form of a flattened, disk-shaped circularcylinder having a length to diameter ratio of about 0.5 or less such asmay most conveniently correspond to the shape of the vehicle steeringwheel.

The diffuser cap portion 316 is in the general form of an inverted bowland includes a top wall 318 and a cylindrical sidewall 320. The sidewall320 includes a plurality of spaced, preferably, generally uniformlyspaced gas exit ports 322. The base portion 314 includes a mountingopening 324 and a peripheral bracket 328 that extends radially outwardfrom the housing 312 and serves to form an interface attachment which isused to attach the inflator assembly 310 to a vehicle, such asidentified above.

The housing 312, similar to the housing 12, is configured to define agenerally cylindrical chamber, here designated by the reference numeral330. The chamber 330 contains or houses a supply of a gas generantmaterial 332, such as composed of a pyrotechnic, such as known in theart, in a desired selected form. A filter assembly 334 such as describedabove surrounds the gas generant material 332.

The inflator assembly 310 includes a retainer 338, a diffuser damper pad340 and a base damper pad 342 which serve as construction expedientssuch as to prevent undesired flow passage through the assembly 310 andavoid undesired rattle or contact of the gas generant 332 within theassembly 310. In practice and such as described above, such damper padelements are commonly composed or fabricated of a glass fiber materialor the like. The inflator assembly 310 differs from the inflatorassembly 10, however, in that the diffuser damper pad 340 is coated withor otherwise contains or includes an igniter composition in accordancewith the invention.

The assembly 310 also includes an adhesive-backed foil seal 344surrounding the filter 334 and generally adjacent the inner surface ofthe sidewall 320 such as to preferably hermetically seal the gasgenerant material 332 within the inflator 310, thereby protecting thegas generant material from possibly damaging ambient conditions, such asincluding moisture.

The inflator assembly 310 further includes an igniter assembly,generally designated by the reference numeral 348, of reducedcomplexity, as compared to the igniter assembly 48 in the prior artinflator assembly 10, described above. The igniter assembly 348 may takethe form of an igniter device or squib 354 and a squib adapter or holder356 whereby the igniter squib 354 is mounted to or is mated with thehousing 312 in a location within the chamber 330 via the mountingopening 324.

When actuated, the squib 354 causes ignition of the igniter materialcoated or otherwise contained or included in or on the diffuser damperpad 340. The products formed or resulting from such ignition are,through the designed configuration, in direct contact with the gasgenerant material 332 contained within the chamber 330 such as to resultin the ignition and reaction of the gas generant material 332. The gasesproduced or formed by such reaction then pass through the filter 334 torupture the foil seal 344 and pass through the gas exit ports 322 andout from the inflator assembly 310 into an associated airbag cushion(not shown).

As will be appreciated, the inflator assembly 310 eliminates the needfor assembly elements such as an igniter cup and/or an igniter tube.Such elimination, in practice, can favorably reduce assembly weight,size and/or performance dependability and thus significantly alter,i.e., reduce, costs such as associated with inflator assemblymanufacture, installation and/or operation, for example.

FIG. 4 shows a simplified view of a dual stage or adaptive inflatordevice or assembly 410, in accordance with one embodiment of theinvention. While the inflator assembly 410 is in many respects similarto the inflator 210 described above, the inflator assembly 410 issignificantly simplified in either or both construction and operation.In particular, the inflator assembly 410 avoids the need for an ignitercup (to hold or contain an igniter material) and an igniter tube(wherethrough products of ignition can be passed through and directedinto contact with an associated supply of gas generant material toeffect ignition and reaction thereof).

The inflator assembly 410, similar to the inflator assembly 210,includes a housing 412 in the general form of a flattened, disk-shapedcircular cylinder having a length to diameter ratio of about 0.5 or lesssuch as may most conveniently correspond to the shape of the vehiclesteering wheel. The housing 412 is formed of a lower shell or baseportion 414 and an upper shell or diffuser cap portion 416.

The diffuser cap portion 416 includes a top wall 418 and a cylindricalsidewall 420. The sidewall 420 includes a plurality of spaced gas exitports 422. The base portion 414 includes first and second mountingopenings, 424 and 426, respectively.

The housing 412 is configured to define a generally cylindrical firstchamber 430 which contains or houses a supply of a first gas generantmaterial 432, such as described above. A filter assembly 434 such asdescribed above surrounds the first gas generant material 432.

Further similar to the inflator assembly 210, the inflator assembly 410also includes a retainer assembly 436 such as composed of a retainer 438and a diffuser damper pad 440. The inflator assembly 410 also may, ifdesired, include a base damper pad (not shown) similar to the basedamper pad 242, shown in FIG. 2. The diffuser damper pad 440, however,is coated or otherwise contains or includes, in accordance with theinvention, with an igniter composition.

The assembly 410 also includes an adhesive-backed foil seal 444surrounding the filter 434 and generally adjacent the inner surface ofthe sidewall 420 such as to preferably hermetically seal the gasgenerant material 432 within the inflator 410, thereby protecting thegas generant material from possibly damaging ambient conditions, such asincluding moisture.

The inflator assembly 410 further includes a first igniter assembly,generally designated by the reference numeral 448, of reducedcomplexity, as compared to the igniter assembly 248 in the prior artinflator assembly 210, described above. The igniter assembly 448 maytake the form of an igniter device or squib 454 and a squib adapter orholder 456 whereby the igniter squib 454 is mounted to or is mated withthe housing 412 in a location within the chamber 430 via the firstmounting opening 424.

The first chamber 430 also houses or contains a second chamber 462 whichsimilar to the chamber 262 in the inflator assembly 210 described aboveincludes a gas generant cup 464, a lid closure 465, a second igniterdevice or squib 466, and a second squib adapter 468 whereby the secondchamber 462 is mounted to or mates with the housing 412 at the secondmounting opening 426.

Similar to the inflator assembly 210, the generant cup 464 and the lidclosure 465 cooperate to form a generant cup interior 470 wherein isdesirably placed a selected quantity of a second gas generant material472. In particular, the generant cup 464 desirably includes a generallycylindrical sidewall 474 which includes a shoulder portion 476 formedtherein and with which the lid closure 465 forms a press or interferencefit form of attachment when in a static state or condition.

When actuated, the squib 454 causes ignition of the igniter materialcoated or otherwise contained or included in or on the diffuser damperpad 440. The products formed or resulting from such ignition are,through the designed configuration, in direct contact with the gasgenerant material 432 contained within the chamber 430 such as to resultin the ignition and reaction of the gas generant material 432. The gasesproduced or formed by such reaction then pass through the filter 434 torupture the foil seal 444 and pass through the gas exit ports 422 andout from the inflator assembly 410 into an associated airbag cushion(not shown).

As with the inflator assembly 310, the inflator assembly 410 inaccordance with the invention eliminates the need for assembly elementssuch as an igniter cup and/or an igniter tube. Such elimination, inpractice, can favorably reduce assembly weight, size and/or performancedependability and thus significantly alter, i.e., reduce, costs such asassociated with inflator assembly manufacture, installation and/oroperation, for example.

While the invention has been described above with respect to inflatorassemblies wherein the ignition material of the invention is coated orotherwise applied on or in a damper pad contained within the inflatorstructure, it will be appreciated that the broader practice of theinvention is not necessarily so limited. For example, in FIGS. 5 and 6,single and dual stage inflator assemblies, 510 and 610, respectively,similar to those described above are shown to identify various possiblesurfaces therewithin that can be appropriately coated or otherwise haveapplied thereto ignition material compositions in accordance with theinvention.

Turning to FIG. 5, in the single stage inflator assembly 510, potentialor candidate surfaces therewithin to which ignition materialcompositions in accordance with the invention can be applied mayinclude, for example and without unnecessary limitation, one or more ofthe following surfaces: the inner surface of the lower shell or baseportion 514, the inner surface of the upper shell or diffuser capportion 516, the gas generant 532, the filter assembly 534; the retainer538, the diffuser damper pad 540 (such as similar to as shown in FIG.3), the base damper pad 542, the squib adapter or holder 556.

FIG. 6 shows that potential or candidate surfaces in the dual stageinflator assembly 610 to which ignition material compositions inaccordance with the invention can be applied include: may includewithout unnecessary limitation one or more of the following surfaces:the inner surface of the lower shell or base portion 614, the innersurface of the upper shell or diffuser cap portion 616, the gas generant632, the filter assembly 634; the retainer 638, the diffuser damper pad640 (such as similar to as shown in FIG. 4), the squib adapter or holder656, the inner surface 664 a of the generant cup 664, the outer surface664 b of the generant cup 664, the inner surface 665 a of the lidclosure 665 and the outer surface 665 b of the lid closure 665, forexample.

The present invention is described in further detail in connection withthe following examples which illustrate or simulate various aspectsinvolved in the practice of the invention. It is to be understood thatall changes that come within the spirit of the invention are desired tobe protected and thus the invention is not to be construed as limited bythese examples.

EXAMPLES Example 1 and Comparative Examples 1 and 2

In each of these tests, 100 grams of igniter composition solids, asshown in TABLE 1, below, was mixed in 100 ml of a selected solvent, asalso shown in TABLE 1, to form a solvent-igniter suspension. (Note: TheAl/Mg alloy had an Al content of 70 weight percent and a Mg content of30 weight percent.)

TABLE 1 IGNITER COMPOSITION (wt. %) TEST SrNO₃ Al/Mg Alloy SiliconeResin SOLVENT Example 1 67.21 30.79 2.00 ethanol Comp. Ex. 1 68.58 32.42— ethanol Comp. Ex. 2 68.58 32.42 — 10% water/ 90% ethanol

The solvent-igniter suspensions of Example 1 and Comparative Examples 1and 2 were then respectively spray applied at high pressure onto thesurface of gas generant tablets of a gas generant formulation composedof 50.38 wt. % guanidine nitrate, 46.62 wt. % basic copper nitrate, 2.70wt. % aluminum oxide, and 0.30 wt. % silicon dioxide. The gas generanttablets were of the following dimensions:

diameter=0.25 in

thickness=0.080 in

In each case, 2.0% by weight of each igniter composition was sprayedonto the tablet surfaces. After spraying the coated tablets were driedunder a stream of hot air.

Example 2 and Comparative Examples 3 and 4

In these tests, the adherence and retention of the coating of theigniter compositions onto gas generant tablets prepared in Example 1 andComparative Examples 1 and 2, respectively, was measured and evaluated.In Example 2, the igniter coated gas generant tablets of Example 1 weretested. In Comparative Examples 3 and 4, the igniter coated gas generanttablets of Comparative Examples 1 and 2, respectively, were tested.

In each test, 50 grams of the respective igniter-coated gas generanttablets were placed on a 25-mesh screen and vibrated at high speed in asieve shaker for 5 minutes. While the severity of such vibration wasextreme, as compared to conditions which might normally be anticipatedfor typical vehicular gas generant-containing inflator installations,such testing was adequate to show relative differences among thesamples.

Following such vibration treatment, the samples are weighed to determinethe amount of weight loss. The weight loss was all attributed to loss ofigniter material from the surface of the gas generant tablets and thepercent of igniter material remaining on the surface was calculated.TABLE 2, below, reports for each of the tests, the percentage of ignitermaterial remaining on the respective gas generant tablets followingbeing subjected to such vibration treatment.

TABLE 2 PERCENTAGE OF IGNITER MATERIAL REMAINING TEST AFTER VIBRATIONExample 2 22.08 Comp. Ex. 3 2.00 Comp. Ex. 4 6.87

Discussion of Results

As the data in TABLE 2 shows, coating the gas generant tablets with thesilicone resin-containing igniter composition in accordance with theinvention, resulted or provided the best (i.e., greatest) retention ofigniter material after subject to the vibration treatment. It is alsonoted that while the water containing solvent mixture used inComparative Example 4 resulted in improved retention of ignitercomposition on the gas generant after vibration as compared to thatresulting Comparative Example 3, the extent of igniter materialretention was still significantly less than that obtained or providedthrough the practice of the invention.

Example 3 and Comparative Example 5

In these tests, the performance of the igniter-coated gas generanttablets of Example 1 and Comparative Example 1 were evaluated. In eachof these tests, 32 grams of the respective igniter-coated gas generanttablets was loaded in an inflator simulator. The inflator simulator wasprovided with a pressure transducer to measure the pressure within thecombustion chamber thereof. The combustion chamber pressure vs. timeperformance was recorded by means of a data collection system. Suchpressure vs. time performance realized with the test inflator device,containing the igniter-coated gas generant tablets of Example 1 andComparative Example 1, respectively, is shown in FIG. 7.

Discussion of Results

As shown by FIG. 7, the performance of the igniter-coated gas generanttablets in Example 3 and Comparative Example 5 were very similar interms of time to first pressure and rise rate. Thus, the data presentedshows that equivalent performance and improved adherence are realized byincorporation of silicone resin binder in the igniter formulation, inaccordance with the invention.

Example 4

In this example, a test inflator device similar in construction to thedual stage or adaptive inflator device or assembly 410 shown in FIG. 4was used. The test inflator device contained 43 grams of a suitable gasgenerant material and the damper pad of the test device was spray coatedwith 1.5 grams of a silicone resin additive-containing ignitercomposition, in accordance with the invention. In particular, theigniter material used was of the following composition:

30.79 wt. % Al/Mg alloy igniter fuel in the form of a solid solutionhaving an Al content of 70 weight percent and a Mg content of 30 weightpercent;

67.21 wt. % strontium nitrate igniter oxidizer; and

2.0 wt. % silicone resin additive.

The test inflator device was mated to a 60-liter steel tank equippedwith a pressure transducer, and the tank pressure vs. time performanceobtained therewith recorded by means of the pressure transducer andassociated data collection system. For purposes of this Example, thetest inflator device was operated in a manner wherein only the firstigniter assembly 448, and not the second igniter device or squib 466,was actuated and fired.

The tank pressure vs. time performance realized with the test inflatordevice is illustrated in FIG. 8.

Discussion of Results

As shown by FIG. 8, the test inflator with the simplified design andconstruction in accordance with the invention, provided tank pressurevs. time performance consistent with desired inflator operation. Thus,through practice of the invention, inflators of desirably simplifieddesign and construction can be used to provide desired operation andperformance.

In view of the above, the invention provides inflator device assembliesand igniter compositions useable therein such that avoid the need forinclusion of hardware such as igniter tubes, igniter cup assemblies orthe like to hold or contain the igniter materials of the inflatordevice. At least partially as a result thereof, the invention providesinflator device assemblies having a design, construction or operation ofincreased simplicity, reduced weight and/or reduced cost.

The invention illustratively disclosed herein suitably may be practicedin the absence of any element, part, step, component, or ingredientwhich is not specifically disclosed herein.

While in the foregoing detailed description this invention has beendescribed in relation to certain preferred embodiments thereof, and manydetails have been set forth for purposes of illustration, it will beapparent to those skilled in the art that the invention is susceptibleto additional embodiments and that certain of the details describedherein can be varied considerably without departing from the basicprinciples of the invention.

What is claimed is:
 1. In an airbag inflator device containing aquantity of gas generant material reactable to produce gas for inflationof an associated inflatable device, the inflator device also containinga quantity of an igniter material reactable to ignite at least a portionof the quantity of gas generant material, the improvement comprising: adamper pad within the inflator device and onto which damper pad at leasta portion of the quantity of igniter material forms a coating.
 2. Theimprovement of claim 1 wherein at least a portion of the damper pad ontowhich the igniter composition forms a coating comprises a glassfiber-based surface.
 3. The improvement of claim 1 wherein the ignitermaterial includes a silicone resin additive effective to adhere theigniter material to the damper pad.
 4. The improvement of claim 3wherein the silicone resin additive has a hydroxyl content in the rangeof about 1% to about 10% by weight and a solubility of at least one gramper 100 ml of organic solvent.
 5. The improvement of claim 4 wherein theigniter material comprises: at least about 10 wt. % and no more thanabout 60 wt. % of an Al/Mg alloy igniter fuel; at least about 30 wt. %and no more than about 80 wt. % of an igniter oxidizer; and at leastabout 1 wt. % and no more than about 10 wt. % of the silicone resinadditive.
 6. The improvement of claim 4 wherein the silicone resinadditive has a solubility of at least one gram per 100 ml of organicsolvent selected from the group of solvents consisting of alcohols,ketones, esters, aromatics and chlorinated organics.
 7. The improvementof claim 1 wherein the igniter material includes a fuel componentcomprising an Al/Mg alloy.
 8. The improvement of claim 7 wherein theAl/Mg alloy contains about 50 to about 90 wt. % Al and about 10 to about50 wt. % Mg.
 9. The improvement of claim 7 wherein the Al/Mg alloy fuelcomponent constitutes between about 10 to about 60 weight percent of theigniter material.
 10. The improvement of claim 1 wherein the ignitermaterial includes an oxidizer selected from the group consisting ofstrontium nitrate, alkali metal nitrates and combinations thereof. 11.The improvement of claim 1 wherein the igniter material includesstrontium nitrate.
 12. The improvement of claim 1 wherein the damper padonto which the igniter material forms a coating is a diffuser damperpad.
 13. The improvement of claim 1 wherein the damper pad onto whichthe igniter material forms a coating is a base damper pad.
 14. Theimprovement of claim 1 wherein the inflator device includes a baseportion and wherein at least a second portion of the quantity of theigniter material forms a coating on an inner surface of the baseportion.
 15. The improvement of claim 1 wherein the inflator deviceincludes a diffuser cap portion and wherein at least a second portion ofthe quantity of igniter material forms a coating on an inner surface ofthe diffuser cap portion.
 16. The improvement of claim 1 wherein atleast a second portion of the quantity of the igniter material forms acoating on at least a portion of the gas generant material.
 17. Theimprovement of claim 1 wherein the inflator device includes a filterassembly contained therewithin and wherein at least a second portion ofthe quantity of igniter material forms a coating on the filter assembly.18. The improvement of claim 1 wherein the inflator device includes aretainer contained therewithin and wherein at least a second portion ofthe quantity of igniter material forms a coating on the retainer. 19.The improvement of claim 1 wherein the inflator device includes a squibadapter contained therewithin and wherein at least a second portion ofthe quantity of igniter material forms a coating on the squib adapter.20. The improvement of claim 1 wherein the inflator device includes agenerant cup contained therewithin.
 21. The improvement of claim 20wherein at least a second portion of the quantity of igniter materialforms a coating on an inner surface of the generant cup.
 22. Theimprovement of claim 20 wherein at least a second portion of thequantity of igniter material forms a coating on an outer surface of thegenerant cup.
 23. The improvement of claim 1 wherein the inflator deviceincludes a generant cup lid closure contained therewithin.
 24. Theimprovement of claim 23 wherein at least a second portion of thequantity of igniter material forms a coating on an inner surface of thegenerant cup lid closure.
 25. The improvement of claim 23 wherein atleast a second portion of the quantity of igniter material forms acoating on an outer surface of the generant cup lid closure.
 26. Theimprovement of claim 1 wherein the inflator device is a single stageinflator assembly.
 27. The improvement of claim 1 wherein the inflatordevice is a dual stage inflator assembly.
 28. In an airbag inflatordevice containing a quantity of gas generant material reactable toproduce gas for inflation of an associated inflatable device, theinflator device also containing a quantity of an igniter materialreactable to ignite at least a portion of the quantity of gas generantmaterial, the improvement comprising: a damper pad within the inflatordevice and onto which damper pad at least a portion of the quantity ofigniter material forms a coating and wherein the igniter materialincludes a silicone resin additive effective to adhere the ignitermaterial to the damper pad, wherein the silicone resin additive has ahydroxyl content in the range of about 1% to about 10% by weight. 29.The improvement of claim 28 wherein the silicone resin additive has asolubility of at least one gram per 100 ml of organic solvent.
 30. Theimprovement of claim 28 wherein the silicone resin additive has asolubility of at least one gram per 100 ml of organic solvent selectedfrom the group consisting of alcohols and ketones.
 31. The improvementof claim 28 wherein the igniter material comprises at least about 1 wt.% of the silicone resin additive and no more than about 10 wt. % of thesilicone resin additive.
 32. The improvement of claim 28 wherein thedamper pad is at least in part-glass fiber-based.
 33. The improvement ofclaim 28 wherein the igniter material includes a fuel componentcomprising an Al/Mg alloy.
 34. The improvement of claim 28 wherein theigniter material includes an oxidizer selected from the group consistingof strontium nitrate, alkali metal nitrates and combinations thereof.35. The improvement of claim 28 wherein the igniter material comprises:at least about 10 wt. % and no more than about 60 wt. % of an Al/Mgalloy igniter fuel; at least about 30 wt. % and no more than about 80wt. % of an igniter oxidizer selected from the group consisting ofstrontium nitrate, alkali metal nitrates and combinations thereof; andat least about 1 wt. % and no more than about 10 wt. % of the siliconeresin additive.